A pharmaceutical injection device is an injection device that holds a pharmaceutical cartridge in its interior, and that is used to inject the pharmaceutical in the pharmaceutical cartridge into a patient's body, etc.
A pharmaceutical injection device may include a main body housing, a piston, and an end stop switch. The main body housing is a member that holds the various members of the pharmaceutical injection device, and forms the exterior of the pharmaceutical injection device. The piston is inserted into a pharmaceutical cartridge to discharge the pharmaceutical inside the pharmaceutical cartridge. The end stop switch is hit by the piston after the piston has been pulled out as far as it will go from the pharmaceutical cartridge. When the piston hits the end stop switch, the end stop switch detects that the piston has been pulled out as far as it will go from the pharmaceutical cartridge. According to this detection result, the stopping device of the pharmaceutical cartridge is disengaged, allowing access for replacing the pharmaceutical cartridge.
In a pharmaceutical injection device, let us assume that a problem has occurred for some reason in the electronic controller used for electrically driving the pharmaceutical injection device. Let us then assume that the end stop switch is unable to operate. If this happens, even when hit by the piston, the end stop switch will not be able to detect that the piston has been pulled out as far as it will go from the pharmaceutical cartridge. Thus, the stopping device of the pharmaceutical cartridge will not be disengaged, and the user will be unable to remove the pharmaceutical cartridge from the pharmaceutical injection device.